首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   683篇
  免费   47篇
  730篇
  2022年   6篇
  2021年   14篇
  2019年   9篇
  2018年   8篇
  2017年   7篇
  2016年   21篇
  2015年   19篇
  2014年   35篇
  2013年   17篇
  2012年   46篇
  2011年   65篇
  2010年   27篇
  2009年   23篇
  2008年   27篇
  2007年   16篇
  2006年   16篇
  2005年   18篇
  2004年   18篇
  2003年   22篇
  2002年   16篇
  2001年   24篇
  2000年   30篇
  1999年   21篇
  1998年   14篇
  1997年   6篇
  1996年   11篇
  1995年   10篇
  1994年   6篇
  1993年   6篇
  1992年   13篇
  1991年   14篇
  1990年   8篇
  1989年   6篇
  1988年   5篇
  1987年   12篇
  1986年   10篇
  1985年   4篇
  1984年   6篇
  1983年   11篇
  1982年   5篇
  1980年   9篇
  1979年   9篇
  1978年   5篇
  1976年   5篇
  1975年   4篇
  1974年   5篇
  1970年   4篇
  1967年   3篇
  1966年   8篇
  1965年   3篇
排序方式: 共有730条查询结果,搜索用时 15 毫秒
721.
Summary A new species of genusPeyronellaea, P. indianensis sp. nov., has been described. Its isolation from the soil is the first record to science. It differs from previously recorded five species parasitizing various host plants. As it is isolated on a filter paper buried in the soil, it is a cellulose decomposing fungus  相似文献   
722.
The change in activity of cinnamic acid 4-hydroxylase (CA4H) in potato parenchyma tissue exposed to various conditions has been examined. Maximum induction of CA4H activity was obtained at 18 hr of incubation. Though CA4H induction can occur in dark, over 100% increase in enzyme activity was obtained on exposure of the tissue to light. Actinomycin D and cycloheximide inhibited the induction process. Mn2+, though known to cause an induction of CA4H in Jerusalem Artichoke, strongly inhibited potato CA4H induction. Dithiothreitol enhanced the CA4H activity due to either activation or protection of the enzyme. CA4H induction was significantly regulated at very low concentrations of trans-cinnamate and paracoumarate.  相似文献   
723.
A strain of Rhizopus stolonifer produced high levels of extracellular ribonuclease (RNase) when grown on YPG (yeast extract, peptone, glucose) medium. Influence of various medium components on the production of extracellular RNase activity showed that divalent metal ions had a marked effect on growth and enzyme production. Maximum enzyme activity (3000 U/ml) was obtained in 5 days when the culture was grown in YPG medium containing Mg2+ (12 mM), Mn2+, and Fe2+ (2 ppm each). Inorganic phosphate, however, repressed enzyme production. Antibodies raised against the purified extracellular RNase were then used to establish the relationship between intra- and extracellular enzymes.  相似文献   
724.
Data on biomass, production and metabolism of the biota, gathered during many years in the Rybinsk Reservoir, USSR, were used to calculate functional interconnections between separate components of the ecosystem, neglecting fluctuations of biomass and postulating a stationary state of the system.A matrix of interconnections was constructed and the influence of an increase or decrease of the biomass of one element upon all other elements of the ecosystem was calculated and discussed.  相似文献   
725.
Summary Catalase in yeast cells is rendered thermolabile on permeabilization using organic solvents or any process of immobilization that eventually permeabilizes the cells. A stable immobilized catalase preparation can be obtained only if yeast cells are immobilized in an intact or viable form.  相似文献   
726.
727.
728.
729.
730.
pH-Dependence of hydrolytic activity of trypsin has been studied in cationic reverse micellar system of cetyltrimethylammonium bromide (CTAB) in (50% v/v) chloroform/isooctane using a positively charged substrate Nα-benzoyl-L-arginine ethyl ester (BAEE). The pH of the medium was varied from 4.0 to 8.5 with addition of 0.025 M citrate-phosphate buffer containing 1 mM CaCl2. Optimum pH for maximum enzyme activity, pHopt in reverse micelles is found to be similar to that observed in bulk aqueous solution (8.0–8.5). However, changes in activity of trypsin (kcat) as a function of water content W0 (W0 = [H2O]/[CTAB]) in reverse micelles are found to be pH dependent. At low pH (4.0) and low water content (W0 = 5) the enzyme is more active in reverse micelles than in bulk aqueous solution by a factor of 2. This ‘superactivity’ is lost at higher W0 values and the kcat in reverse micelles is found to be similar to that observed in aqueous bulk. At pH 5, the enzyme activity is found to be independent of W0 while at pH 6.0–6.5 the enzyme activity is low at W0 5 and increases with water content to a constant value which is still 50% lower than that in aqueous buffer. Above pH 7, the Wo-activity profile becomes distinctly bell shaped with W0 optimum around 10–15. The enzyme activity at optimum W0 is close to that observed in aqueous bulk.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号